Connected: An Internet Encyclopedia
RFC 1725 - 5. The TRANSACTION State

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### 5. The TRANSACTION State

Once the client has successfully identified itself to the POP3 server and the POP3 server has locked and opened the appropriate maildrop, the POP3 session is now in the TRANSACTION state. The client may now issue any of the following POP3 commands repeatedly. After each command, the POP3 server issues a response. Eventually, the client issues the QUIT command and the POP3 session enters the UPDATE state.

Here are the POP3 commands valid in the TRANSACTION state:

          STAT

             Arguments: none

             Restrictions:
                 may only be given in the TRANSACTION state

             Discussion:
                 The POP3 server issues a positive response with a line
                 containing information for the maildrop.  This line is
                 called a "drop listing" for that maildrop.

                 In order to simplify parsing, all POP3 servers required to
                 use a certain format for drop listings.  The positive
                 response consists of "+OK" followed by a single space, the
                 number of messages in the maildrop, a single space, and the
                 size of the maildrop in octets.  This memo makes no
                 requirement on what follows the maildrop size.  Minimal
                 implementations should just end that line of the response
                 with a CRLF pair.  More advanced implementations may
                 include other information.

                    NOTE: This memo STRONGLY discourages implementations
                    from supplying additional information in the drop
                    listing.  Other, optional, facilities are discussed
                    later on which permit the client to parse the messages
                    in the maildrop.

                 Note that messages marked as deleted are not counted in
                 either total.

             Possible Responses:
                 +OK nn mm

             Examples:
                 C: STAT
                 S: +OK 2 320

          LIST [msg]

             Arguments:
                 a message-number (optional), which, if present, may NOT
                 refer to a message marked as deleted

             Restrictions:
                 may only be given in the TRANSACTION state

             Discussion:
                 If an argument was given and the POP3 server issues a
                 positive response with a line containing information for
                 that message.  This line is called a "scan listing" for
                 that message.

                 If no argument was given and the POP3 server issues a
                 positive response, then the response given is multi-line.
                 After the initial +OK, for each message in the maildrop,
                 the POP3 server responds with a line containing information
                 for that message.  This line is also called a "scan
                 listing" for that message.

                 In order to simplify parsing, all POP3 servers are required
                 to use a certain format for scan listings.  A scan listing
                 consists of the message-number of the message, followed by
                 a single space and the exact size of the message in octets.
                 This memo makes no requirement on what follows the message
                 size in the scan listing.  Minimal implementations should
                 just end that line of the response with a CRLF pair.  More
                 advanced implementations may include other information, as
                 parsed from the message.

                    NOTE: This memo STRONGLY discourages implementations
                    from supplying additional information in the scan
                    listing.  Other, optional, facilities are discussed
                    later on which permit the client to parse the messages
                    in the maildrop.

                 Note that messages marked as deleted are not listed.

             Possible Responses:
                 +OK scan listing follows
                 -ERR no such message

             Examples:
                 C: LIST
                 S: +OK 2 messages (320 octets)
                 S: 1 120
                 S: 2 200
                 S: .
                   ...
                 C: LIST 2
                 S: +OK 2 200
                   ...
                 C: LIST 3
                 S: -ERR no such message, only 2 messages in maildrop

          RETR msg

             Arguments:
                 a message-number (required) which may not refer to a
                 message marked as deleted

             Restrictions:
                 may only be given in the TRANSACTION state
             Discussion:
                 If the POP3 server issues a positive response, then the
                 response given is multi-line.  After the initial +OK, the
                 POP3 server sends the message corresponding to the given
                 message-number, being careful to byte-stuff the termination
                 character (as with all multi-line responses).

             Possible Responses:
                 +OK message follows
                 -ERR no such message

             Examples:
                 C: RETR 1
                 S: +OK 120 octets
                 S: <the POP3 server sends the entire message here>
                 S: .

          DELE msg

             Arguments:
                 a message-number (required) which may not refer to a
                 message marked as deleted

             Restrictions:
                 may only be given in the TRANSACTION state

             Discussion:
                 The POP3 server marks the message as deleted.  Any future
                 reference to the message-number associated with the message
                 in a POP3 command generates an error.  The POP3 server does
                 not actually delete the message until the POP3 session
                 enters the UPDATE state.

             Possible Responses:
                 +OK message deleted
                 -ERR no such message

             Examples:
                 C: DELE 1
                 S: +OK message 1 deleted
                    ...
                 C: DELE 2
                 S: -ERR message 2 already deleted

          NOOP

             Arguments: none

             Restrictions:
                 may only be given in the TRANSACTION state

             Discussion:
                 The POP3 server does nothing, it merely replies with a
                 positive response.

             Possible Responses:
                 +OK

             Examples:
                 C: NOOP
                 S: +OK

          RSET

             Arguments: none

             Restrictions:
                 may only be given in the TRANSACTION state

             Discussion:
                 If any messages have been marked as deleted by the POP3
                 server, they are unmarked.  The POP3 server then replies
                 with a positive response.

             Possible Responses:
                 +OK

             Examples:
                 C: RSET
                 S: +OK maildrop has 2 messages (320 octets)

Next: 6. The UPDATE State

Connected: An Internet Encyclopedia
RFC 1725 - 5. The TRANSACTION State